Outcomes	Relative effect (95% CI)	No of Participants (studies)	Quality of the evidence (GRADE)	Comments
Low birthweight (less than 2500 g)	RR 0.96 (0.61 to 1.52)	1111 (7 studies)	⊕ ○ ○ ○ very low 1
Birthweight (g)	MD −8.62 (−52.76 to 35. 52)	1152 (8 studies)	⊕ ○ ○ ○ very low 2
Premature birth (less than 37 weeks of gestation)	RR 1.82 (0.75 to 4.40)	382 (4 studies)	⊕ ○ ○ ○ very low 3
Neonatal death (death within first 28 days of life)	Not estimable	0 (0)	See comment	No studies reported data for this outcome.
Congenital anomalies (including neural tube defects)	Not estimable	0 (0)	See comment	No studies reported data for this outcome.

CI: Confidence interval; RR: Risk ratio.

GRADE Working Group grades of evidence

High quality: Further research is very unlikely to change our confidence in the estimate of effect.

Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.

Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.

Very low quality: We are very uncertain about the estimate.

¹Six of the studies contributing data had high levels of attrition, none had blinding and five had high or unclear risk of bias for allocation concealment. Proportion of events was low and there was some imprecision in the estimate. The results were consistent and statistical heterogeneity was nil (I² = 0%).

²Seven of the studies contributing data had high levels of attrition, none had blinding and five had high or unclear risk of bias for allocation concealment. 95% confidence intervals were wide for this outcome, although the results were consistent and statistical heterogeneity was nil (I² = 0%).

³Three of the included studies had high attrition, lacked blinding and five had unclear of high risk of bias for allocation concealment. Proportion of events was low. The results were consistent and statistical heterogeneity was nil (I² = 0%).